This invention relates to low-pressure casting apparatus of the type described in U.S. Pat. No. 3,757,850. A holding furnace is adapted to be closed gas-tightly, to be supplied with a compressed gas and to hold a metal bath. A riser pipe immersed in the bath connects the furnace to the base plate of a permanent mold which consists of stationary or fixed mold parts. The mold is adapted to be closed at it top by a core cover plate which carries on its underside the core affixed thereto. The cover plate is vertically movable by means of a plurality of hydraulically operated tension columns. The casting apparatus also includes two opposed flat vertical beams which are attached to rear portions of the sides of the holding furnace housing. The furnace is closed by a cover which carries the base plate of the permanent mold. A horizontal bridge structure, which has a forwardly opening, U-shaped recess is mounted between the vertical beams and includes forwardly and rearwardly projecting arms. A horizontally movably, hydraulically operated tension element is mounted in the U-shaped recess and serves to operate tension columns, as described and shown in U.S. Pat. No. 3,757,850.
This low-pressure casting apparatus affords a number of important advantages. For instance, the stroke length of the tension columns can be adjusted by a simple and fast operation to the overall height of the parts of the permanent mold because the bridge structure is vertically movably mounted on the vertical beams. Besides, the attachment of the vertical beams to the rear portion of the sides of the holding furnace housing and the U-shaped recesses in the bridge structure allow installation of the parts of the permanent molds, and replacement of the riser pipe in a vertical direction from above, in a simple operation without substantial physical effort and without having to remove mold attaching devices from the holding furnace.
The tension element which is horizontally movably mounted in the U-shaped recess of the bridge structure makes it possible to drop castings suspended from the core cover plate directly onto handling means positioned between the flat beams, e.g., a chute, so that it is no longer necessary for the operator to remove the casting from the core cover plate and to deposit it in a handling container.
According to an additional feature of the low-pressure casting apparatus, the brackets holding the bridge structure are clamped to the flat beams by a plurality of clamp screws when the apparatus is in operation. If a change in the parts of the permanent mold requires a change of the length of the stroke of the tension columns, the clamp screws are loosened. Thus, the bridge structure is held in position on the flat beams by clamping bars, which act on the rear edges of the flat beams under a certain spring pressure, the clamping bars being connected to the bridge structure by the spring.